1. Field of the Invention
The present invention relates in general to an electrical/biological interface sensor and, in particular, to a sensor and method capable of detecting an air borne or exogenously introduced analyte including, for example, a hazardous chemical.
2. Description of Related Art
Manufacturers of electrical/biological interface sensors have been trying to design such sensors that are both reliable and easy to assemble. An electrical/biological interface sensor is basically a sensor incorporating a biosensor that can transform a biological process into an electrical output when it detects a specific analyte (e.g., hazardous chemical). Examples of traditional electrical/biological interface sensors are briefly discussed below and described in PCT Patent Application No. WO 00/25121 which is hereby incorporated by reference herein.
Referring to FIGS. 1A and 1B (PRIOR ART), there are respectively illustrated a side view and a top view of a traditional sensor 100 described in the aforementioned PCT Patent Application No. WO 00/25121. This traditional sensor 100 is fabricated as a chip and has an electrically insulating barrier defined by a silicone substrate 102 and a thin film insulating layer 104 (e.g., silicone nitride) positioned in electrical communication with an electrical circuit 118, 120 and 122. The electrical circuit 118, 120 and 122 is constructed and arranged to detect changes in the electrical characteristic of an ion channel(s) in a hole 110 covered by a lipid bilayer of the insulating layer 104 which is positioned between two electrolytes 106 and 108.
The two electrolyte containers 112 and 114 are constructed to contain electrolytes 106 and 108, respectively, and to position the electrolytes 106 and 108 in contact with different sides of the insulating layer 104. Container 112 includes a passageway 116 that allows exposure of electrolyte 106 to an analyte. In some cases, the containers 112 and 114 can be removed from and reattached to the electrically insulating barrier 102 and 104 using an adhesive, snap-fit, auxiliary fasteners or the like.
Electrical circuitry 118, 120 and 122 is provided to electrically contact the electrolytes 106 and 108 in containers 112 and 114. As illustrated, a positive bias electrode 118 is partially immersed in the electrolyte 106 and a negative bias electrode 120 is partially immersed in the electrolyte 108. FIG. 1A depicts electrode 120 as being positioned adjacent to one side of insulating layer 104, and electrode 118 is shown as being positioned against the silicon substrate 102 which in turn is positioned against the insulating layer 104. The electrodes 118 and 120 can be connected to an integrated circuit amplifier and bias generator 122 that indicates the presence of an analyte in response to a change in the electrical characteristic of the ion channel(s).
Referring to FIGS. 2A and 2B (PRIOR ART), there are respectively illustrated a disassembled side view and an assembled side view of another traditional sensor 200 described in the aforementioned PCT Patent Application No. WO 00/25121. This traditional sensor 200 includes a barrier 202 having a top side 204 and a bottom side 206 as oriented in the illustrations. The barrier 202 is based upon an annular silicon ring 208 that tapers, at its center, to a relatively large hole. A silicon nitride thin film layer is provided on the bottom side of the silicon ring 208 which includes a hole 210 at its center, concentric with the hole in the center of the silicon ring 208, but much smaller, on the order of 1 micron or less. The silicon nitride thin film layer extends centrally into the hole in the silicon ring 208 and defines part of the electrically insulating barrier. Although, not shown, within hole 210 is a lipid bilayer membrane including an ion channel(s). An electrically insulating layer 212 covers the top side 204 of the silicon ring 208 and extends centrally beyond the silicon ring 208 into the hole within the silicon ring 208 and onto the silicon nitride thin film layer but does not extend to hole 210. Thus, the silicon ring 208, the silicon nitride thin film layer and the electrically insulating layer 212 define the barrier 202.
The tapering portion within the center of the silicon ring 208 is suitable for receiving an electrolyte solution 214. Below the bottom side 206 of the barrier 202 is provided a bottom component 216 which includes a center receptacle 218 positioned for alignment with the hole 210. The receptacle 218 contains an electrode 220 (e.g., silver) and is suitable for receiving a second electrolyte solution 222.
The traditional sensor 200 also includes a top portion 224 having a second electrode 226 (e.g., silver) positioned in or near the center thereof. The bottom portion 216 and the top portion 224 are constructed of an electrically insulating material and designed to snap-fit together, sandwiching therebetween the middle portion including the barrier 202. Seals, such as Sylgard(copyright) seals 228 can be provided to mate with portions of the bottom portion 216 and the top portion 224 to create isolated chambers containing the electrolytes 214 and 222 immediately above and below the hole 210.
When the traditional sensor 200 is assembled, the electrolytes 214 and 222 are brought into contact with opposite sides of the hole 210, thus in contact with opposite sides of the ion channel(s) (not shown) within the hole 210. Electrical circuitry (not shown) connects electrodes 220 and 226 and indicates the presence of the analyte in response to a change in the electrical characteristic of the ion channel(s). In other words, when the traditional sensor 200 is exposed to air containing the analyte which passed through passages 230 and diffused through electrolyte 214 and then binded to a pore(s) of the ion channel(s) within hole 210 its presence can be sensed by the electrical circuitry.
Referring to FIGS. 3A and 3B (PRIOR ART), there are respectively illustrated a sectional side view and top view of yet another traditional sensor 300 described in the aforementioned PCT Patent Application No. WO 00/25121. This traditional sensor 300 includes a barrier 302 separating electrolytes 304 and 306 within bottom and top containers 308 and 310, respectively, defined by the connection of bottom component 312 and top component 314, respectively, to barrier 302. As illustrated, the bottom component 312 defines, itself, an electrode addressed by an electrical lead 316, and top component 314 defines, itself, an electrode addressed by an electrical lead 318. Electrolyte solution 304 completely fills the bottom container 308, but electrolyte solution 306 only partially fills the top container 310, the remainder of which is filled with air. This partially assists in compensating for expansion and contraction of the electrolyte solution 306. Electrical leads 316 and 318 can connect to electrical circuitry (not shown) that is similar to the electrical circuitry described above with respect to traditional sensors 100 and 200.
The barrier 302 includes a central portion 320 that is electrically insulating and flexible enough to adjust for thermal expansion and contraction of the electrolyte solution 304 in the bottom container 308 to the extent that electrolyte solution 304 can completely fill the bottom container 308 without void space. The top component 314 includes a central passageway 322 used to introduce the electrolyte solution 306 into the top container 310 such that the electrolyte solution 306 is in contact with a thin film 324. The top component 314 also includes peripheral passages 326 that allow introduction of analyte-containing fluid (e.g. air) into the top container 310 for diffusion through the electrolyte solution 306 into contact with a pore(s) mounted within the thin film 324. The thin film 324 includes a nanoscale hole covered by a lipid bilayer having an ion channel(s) which defines the pore(s).
Unfortunately, the traditional sensors 100, 200 and 300 are not real working models but instead are conceptual models or prototype models used only for experimentation and research. Accordingly, there is a need for a sensor that is easy to assemble and can operate effectively to detect an air borne or exogenously introduced analyte. This need and other needs are satisfied by the sensor and method of the present invention.
The present invention includes a method and sensor that is easy to assemble and can operate to effectively detect an air borne or exogenously introduced analyte. In one embodiment, the assembled sensor includes a top cap capable of receiving a first electrolyte and a bottom cap capable of receiving a second electrolyte. The assembled sensor also includes a flexible boot that holds together the top cap, the bottom cap and a biosensor. The biosensor is operational when it is located between the first electrolyte and the second electrolyte and enables an electrical device to detect an analyte (e.g., hazardous chemical) that enters the sensor through a passage in the top cap. In particular, the electrical device can apply a voltage to the first electrolyte, the biosensor and the second electrolyte, and then detect the presence of an analyte interacting with the bibsensor by detecting a change in the electrical characteristic of the biosensor caused by the presence of the analyte. Several different configurations and embodiments of the sensor all of which are easy to assemble and all of which can operate effectively to detect an analyte are described below.